Both terms refer to driving or operating a motor vehicle while under the influence of drugs or alcohol. The term DWI stands for Driving While Impaired and the term DUI stands for Driving Under the Influence. In the United States, the country wide legal limit for blood alcohol is .08; however individual states differ in how this rule is enforced; DWI is a more serious charge and DUI is a less serious charge. For example, if you have been charged with DWI and it is your first offense, and you are appropriately remorseful, the charge could be reduced to a DUI which carries lower penalties. Other states make no distinction. If you are above the legal limit, you are charged whether it is your first offense or not; this is known as a Zero Tolerance policy. Another differentiation is made by some states: DUI refers to Driving Under the Influence of Drugs, while DWI refers to alcohol. The drugs in this case could be legal or illegal.
In Europe, the laws are more relaxed, but there social norms keep these offenses to a minimum.
In Canada, no distinction is made and the terms are used interchangeably. The legal limit is .08, as in the U.S. There is a lesser charge, if the court can be persuaded that results in no criminal record, minimal to no jail time and minimal to know prohibition against driving. This is known as Driving Without Due Care and Attention or Driving Without Consideration.
There are various studies examining the affect that drugs have on driving ability; especially since there has been such an increase in people taking anti anxiety or antidepressant information. Legal limits are being set for such substances as Ativan and pseudoephedrine.
Bottom line in my opinion: it is not worth risking ruining the life of innocent strangers, your own life, your kid’s lives and the lives of any of your potential victims just to save money on cab fare home.